The present invention relates to an apparatus and a method of generating compressed data that compresses and encodes imputted data and outputs the compressed data generated through the compression and encoding process to communication media.
Advances in digital techniques have allowed practical utilization of a multimedia system. The multimedia system is defined as a system for integrational handling of multiple representation media (video data, audio data, additional data and so on) with a single communication medium (a telecommunication medium, a storage medium, a broadcast medium and so on).
The multimedia system includes a digital video disk (DVD) authoring system and a digital satellite broadcasting system. The DVD authoring system is a system for recording multiple representation media such as video data (referred to as xe2x80x98material dataxe2x80x99 in the following description) in a unified form on a single DVD (a storage medium). The digital satellite broadcasting system is a system for broadcasting program data of multiple channels (data made up of a plurality of material data) in a unified form through a single communications line (a broadcast medium).
In order to implement such a multimedia system, an apparatus for generating compressed data is required for compressing and encoding material data such as video data and outputting the compressed data generated through the compression and encoding process to a communication medium.
The apparatus for generating compressed data requires: a means for compressing and encoding material data to generate compressed data; a means for outputting the compressed data generated through the compression and encoding process to a communication medium; and a means for transferring the compressed data to the means for outputting.
FIG. 12 is a block diagram showing a related-art apparatus for generating compressed data comprising the three means described above. FIG. 12 illustrates an output of compressed data obtained through a compression and encoding process to a communication medium wherein the compressed data is outputted to the communication medium as it is.
The compressed data generating apparatus 10 comprises: a video encoder 11 (1); an audio encoder 11 (2); a subtitle encoder 11 (3); a small computer system interface (SCSI) 12; a central processing unit (CPU) 13; a random access memory (RAM) 14; a read only memory (ROM) 15; and a CPU bus 16.
The encoders 11 (1) to 11 (3) have compression and encoding sections 111 (1) to 111 (3) and output buffers 112 (1) to 112 (3). The compression and encoding sections 111 (1) to 111 (3) constitute the means for compressing and encoding described above. The SCSI interface 12 constitutes the means for outputting described above. The means for transferring described above is made up of the output buffers 112 (1) to 112 (3), the CPU 13, the ROM 14, the RAM 15 and the CPU bus 16.
In the apparatus 10, video signal VS, audio signal AS and subtitle signal SS of one program are each individually compressed and encoded at the corresponding compression and encoding sections 111 (1) to 111 (3) of the encoders 11 (1) to 11 (3) to be written into the output buffers 112 (1) to 112 (3), respectively.
The compressed data written into the output buffers 112 (1) to 112 (3) is transferred to the RAM 14 by the CPU 13 through the CPU bus 16. The compressed data transferred to the RAM 14 is transferred to the SCSI interface 12 by the CPU 13 through the CPU bus 16. Streams of data transferred to the SCSI interface 12 are supplied to a digital storage medium (DSM) 20 according to the SCSI protocol.
The CPU 13 controls reading of the compressed data from the output buffers 112 (1) to 112 (3) based on remaining space in the output buffers 112 (1) to 112 (3). The remaining space in the output buffers 112 (1) to 112 (3) is determined based on data size information indicating a size of the compressed data. The data size information is generated at the compression and encoding sections 111 (1) to 111 (3) to be sent to the RAM 16 by the CPU 15 through the CPU bus 18.
As described so far, the related-art apparatus 10 for generating compressed data allows the CPU 13 to perform both of the process for compressed data transfer and the process for controlling the data transfer process. In other words, the related-art apparatus 10 transfers both compressed data and control data such as data size information through the CPU bus 16.
In the configuration, however, compressed data and control data concentrate on the CPU bus 16. A traffic on the CPU bus 16 thus increases. Consequently, limitations are imposed on transfer of compressed data and control data.
It is therefore impossible for the related-art apparatus 10 to provide real-time generation of compressed data. It is also required that capacities of the output buffers 112 (1) to 112 (3) be enlarged.
Another problem is that the apparatus 10 not capable of providing real-time generation of compressed data is not applicable to the multimedia system requiring real-time processing.
It is an object of the invention to provide an apparatus for generating compressed data and a method of generating compressed data wherein limitations are reduced on transfer of compressed data and control data due to an increase in traffic.
An apparatus for generating compressed data of the invention comprises: a compression and encoding means for compressing and encoding input data and outputting the data; an output means for outputting the compressed data outputted from the compression and encoding means; a data transfer means for transferring the compressed data outputted from the compression and encoding means to the output means; and a control means connected to the compression and encoding means through a control bus for performing control for inputting the compressed data outputted from the compression and encoding means to the data transfer means based on control information from the control bus.
In the apparatus, the input data is compressed and encoded by the compression and encoding means and outputted. The compressed data outputted from the compression and encoding means is controlled by the control means to be inputted to the data transfer means based on the control information from the control bus. The compressed data inputted to the data transfer means is transferred to the means for outputting. The compressed data transferred to the means for outputting is supplied to a communication medium by the means for outputting.
The data transfer process of the compressed data performed by the data transfer means is controlled by the control means through the control bus different from the data transfer bus. As a result, limitations are reduced on transfer of compressed data and control data due to an increase in traffic.
A method of generating compressed data of the invention includes: a step of compressing and encoding input data by a compression and encoding means; a transfer control step of receiving control information on the compressed data compressed and encoded in the step of compressing and encoding through a control bus and controlling transfer of the compressed data based on the received control information; a data transfer step of transferring the compressed data compressed and encoded in the step of compressing and encoding based on the transfer control step; and a step of outputting the compressed data transferred in the data transfer step to outside.
In the method, the input data is compressed and encoded in the step of compressing and encoding. The control information for the compressed data is received through the control bus in the transfer control step. Based on the control information, the transfer of the compressed data is controlled in the transfer control step. Based on the transfer control step, the compressed data is transferred in the data transfer step. The compressed data transferred in the data transfer step is outputted to outside in the step of outputting.
The data transfer process is controlled through the bus different from the data transfer bus. As a result, limitations are reduced on transfer of compressed data and control data due to an increase in traffic.